The supernatural power that a believer may use must (and can only) come from God. I would never deny this.
What I was attempting to propose is that this supernatural power which comes directly from God could be called "magic", because supernatural power falls within the definition of magic. If this could be the case, then Authors like C.S. Lewis were not committing blasphemy by associating God with magic.
Again, the problem with your definition refering to the Lord's power is the word "uses". Can one "use" God's power the way magic is used?